The present invention relates to improvements in film advancing or winding mechanisms having utility in still cameras for advancing the roll film used in such cameras by the length of one frame between successive exposures of the film, and is an improvement over the film winding mechanism disclosed in U.S. Pat. No. 4,032,940.
The film advancing mechanism is shown in this patent as part of a pocket size retractable camera made in two sections, one being a main camera section including all of the operating elements of the camera except for the viewfinder carrying section thereof. The viewfinder carrying section forms a separate section mounted on the end of the main camera section for sliding movement between a retracted inoperative position and an extended operative position. The viewfinder carrying section of the camera is coupled to the film advancing mechanism of the camera which enables film advance to take place only when the viewfinder carrying section is moved to its extended, operative position. Shutter cocking occurs during the retraction of the viewfinder carrying section to its inoperative position. The viewfinder carrying section of the camera also is provided with means for removing a film sensing pawl or finger from a metering aperture in the film when the viewfinder carrying section is moved to its retracted position. Film advance occurs during movement of the viewfinder carrying section to its extended position when the film metering pawl is removed from the film metering aperture of the film.
The film winding mechanism disclosed in this patent includes a planetary gear mechanism, which permits the reciprocable viewfinder carrying section of the camera housing to be moved fully to its extended position after the film metering pawl enters a film aperture to terminate a film winding operation. To this end, the planetary gear mechanism disclosed in this patent includes a sun gear carried by the center portion of a ratchet wheel which is normally held in place by a locking pawl. The sun gear meshes with at least one eccentric gear carried by a drive gear which moves in one direction or the other, depending upon the direction of movement of the viewfinder carrying section of the camera. When the ratchet wheel is locked in place, the extended movement of the viewfinder carrying section of the camera imparts rotation to the drive gear which, in turn, bodily rotates the eccentric gear carried thereby,which drivingly engages the inner gear teeth of an annular film winding gear to effect a film winding operation. When the film metering pawl enters the film aperture and the film moves the metering pawl a small distance, this effects the release of a locking pawl from the ratchet wheel so that the sun gear carried thereby is free to rotate. The free rotation of the sun gear effectively decouples the bodily movement of the eccentric gear from driving action with the annular film winding gear, so that the viewfinder section can be moved to its fully extended position and then returned to its initial retracted position where shutter cocking and other operations can be carried out. To avoid tearing of the film when the film is completely unwound from the supply spool, the drive gear forms part of a slip clutch which enables the viewfinder section to be moved fully between its extreme positions even when the annular gear and the sun gear carrying ratchet wheel are locked against rotation.
The present invention represents a re-design and simplification of this planetary gear and film winding mechanism which reduces the number of parts therein. The slip clutch mechanism heretofore used is replaced by a much simpler one comprising a sun gear-carrying member and a ratchet wheel continuously held against rotation in one direction and forming a friction slip clutch with the latter member. Film winding is terminated by a locking pawl positively locking the aforesaid annular gear. In accordance with preferred specific aspects of the invention, the sun gear is carried by a rotatable member which confronts the ratchet wheel. The sun gear-carrying member preferably has or is connected to a member with projecting portions adapted to enter and normally be held by locking recesses formed in an axial face of the ratchet wheel. These projecting means can slip out of the recesses of the ratchet wheel when the annular gear is locked against rotation. When the viewfinder section of the camera is retracted and the drive gear carrying the eccentric gear is bodily rotated thereby, the sun gear and slip clutch-forming member carrying the same is rotated to bring the aforesaid projecting means once again into the locking recesses in the ratchet wheel which is free to rotate, because the aforesaid locking pawl permits such rotation in one direction.
The above and other features and advantages of the invention will become apparent upon making reference to the specification to follow when taken in conjunction with the accompanying drawings.